Knoppix Bootup Problems

I downloaded the Iso for Knoppix and Burn it to a CD when I go to boot into it everything seem fine I get the knoppix Splash screen and the boot: but when I hit enter I get this message something like

Uncompressing Linux...

Invaild Compression Format (err=1)

System Halted--


Could somebody tell me what I did wrong and How to fix it.

Offhand, I'd say the iso was scrambled a bit during either the burning or the downloading. For the former, check your buring software for a "compare" option, or just re-burn the CD. For the latter, use md5sum to check the .iso.